High output vapor generator for aircraft



Dec. 3, 1940. N c PR|CE 2%223i856 HIGH OUTPUT VAPOR GENERATOR FORAIRCRAFT Filed July 13, 1938 5 Sheets-Sheet 1 'FILE -.:L A

INVENTOR 1 Dec. 3, 1940. pmcE 2,223,856

' HIGH OUTPUT VAPOR GENERATOR FOR AIRCRAFT Filed July 15, 1938 5Sheets-Sheet 2 INVENTOR Dec. 3, 1940. c p cg 2,223,856

HIGH OUTPUT VAPOR GENERATOR FOR AIRCRAFT Filed July 13, 1938 5Sheets-Sheet 3 SPEED FIE-dlNVENTOR Dec. 3, 1940. v c PR|CE 2,223,856

HIGH QUTPUT.'VAPOR GENERATOR FOR AIRCRAFT Filed Jdl 13, 1938 sSheets-Sheet 5 "JNIGHD 301.4

Patented Dec. 3, 1940 UNITED STATES PATENTTOFF/ICE man oorro'r v afifnnnna'ron For. 7

Nathan C. Price, Seattle, Wash. Application July 13, 1938, Serial No.218,942: 3 Claims- (Cl. 122-451) The invention primarily relates tovapor generators for use in aircraft, for in that application it is ofthe greatest importance to have power plants which are light, compact,and efll- 5 cient. The invention satisfactorily meets these requirementsand furthermore provides a type of vapor generator which is veryflexible from performance standpoints and practically unafiected bychange of operational altitude.

However the suitability of the generator is not limited to aircraftalone. It is of value for boats, locomotives, stationary power plants,and the like, but in the aircraft application its advantages be, comemost fully realized.

Accordingly it is an object of the invention to provide a vaporgenerator capable of extremely high output notwithstanding the fact thatthe generator is very compact, light, and efllcient.

It is an objective to supply a type of generator which incorporates anintegral set 0! generation accessories related and constructed as topermit extremely high rates of fluid flow to be produced in thegeneration system for lightness and efllciency.

These and other allied objectives are indicated in the specificationpresented herewith and in which:

Figure 1 is a section through the principal axis of a representativeform of the generator.

" Figure 2 is a section through the axis of a feed pump of thegenerator. I prefer to call this mechanism a loading pump because it isused to charge a second stage feed pump of special form shown in sectionin Figure 4.

diffuser of the loading pump.

Figure 5 is "a diagrammatic representation of the flmctionalrelationships of the various elements of the vapor generator.

Figure 6 is a chart of pressures and temperatures of the combustionsystem of the generator.

Certain power plant auxiliaries such as the feedwater pump, fuel pump,lubrication pump, vacuum pump, and blower, ordinarily considered to bedistinct and separate from the generator are in this instance classifiedas parts of the vapor generator, for they are actually built into thegeneration.

50 I have succeeded in producing a weight ratio of the complete steamgenerator of the identified type, below .35 lb. weight per power plantbrake horsepower in a size suitable for a 5000 horsepower propulsionturbine. The compactness can also be illustrated by actual overalldimensions.

Figure 3 is a section through the impeller and The generator is about 24inches in diameter and about 75 inches long in the specified case.

The generator air, combustion gas and vapor flow systems utilizevelocities of high value. 1500 It. per second velocity isrepresentative. This 5 results in a very high rate of heat transfer andin the most compact boiler structure, because the heat transfer surfacesare made many times more effective than in-the ordinary vapor generator.The space required for passage of the air, gas, and 10 vapor is verysmall because of the high rate of motion. i

In general the heat transfer surfaces of the generator, the combustionchamber, the burner,

the air preheater, the blower, the blower diil'user, l5

and various other parts of the generator are constructed andinterrelated in substantial accordance with the presentation of mycopending patent Serial No. 120,188, flied Jan. 12, 1937, and entitled"Fluid heater."

The variation in air density with change of aircraft operationalaltitude requires a variable power for operating the boiler blower,which must be rotated faster at the higher altitudes. In the inventionit is deemed preferable to maintain sub- 25 stantially constantcombustion chamber pressure regardless of altitude, at each given powerplant output. The generator 0;! the described type is structuralllycapable of withstanding the high internal combustion gas pressure andthe very high rates of flow, because it is intrinsically pressureresistant due to its cylindrical shape. Fur thermore the flow passagesare so direct that very high velocities may be produced without ex-'-cessive flow resistance.

At sea level the pressure in the combustion chamber may for instance .belbs. per square inch absolute at full power, and at normal operationalaltitude where the atmosphere density is only a fraction of that at sea.level the pressure 40 in the combustion chamber is still maintained atapproximately 35 lbs. per square in h absolute.

The power for operating the air blower for the boiler is largely orentirely derived from an exhaust gas turbine interposed between thefinal gas sweep of the economizer section and the atmosphere. At sealevel a 10 lbs. per square inch pressure drop is suflicient foroperating the turbine and the remaining 10 lbs. per square inch pressuredrop is available for forcing the gases past the heat transfer surfaces.At altitude only 10 lbs. per square inch pressure drop for instance isagain used for forcing the gases past the heat transfer surfaces, whichallows a relatively large pressure drop for operating the gas turbine.Thus 5,0high temperature and pressure. The emciency 06 flclency oi thegenerator and decreasesstructural as the power and blower speedrequirements become greater, the power available appropriately Due tothe large expansion through the gas turbine, very low flue gastemperatures, as 260' F. ror.instance, are produced without necessityfor large economizer section and without large airpreheaters. r Thecombustion gas expansion in a turbine inq creases the efliciency oi thepower plant cycle roim s s a the waterwfld not be heated then the powerfor driving the -generator accessin the desired Way by bled 01! Workingp r -y componentsneed be derived, ,4; 1 from the turbine. Furthermorethe pump would not be fully derived from the main working fluid be s 1being generated m the boner tuba A reciprocating pump .is likewisedisadvanta- The utilization of power. of the gas turbine at w 1mm sizeend'weilht etendmmtef the boiler'combustion 'gas outlet likewise permitsl invent! the feed Pumping system the eiilciency oi the pump low as aresult. Due to the large number 0! stages and to the high peripheralvelocity of each impeller, the water. in

representative case at least 3200lbs. per square inch pressure.Attainment or such pressure'by means of a centrifugal or velocity typepump would require a number of high speed impellers. in series. Theviscous losses would be great and the pump would become considerablyheated by a u degree of working-vapor regeneration; the vapor generatoris composed ottwo separate 'rature flue M m then no longer intimatelyrelated pumping a easea t: the atmosghere by virtue 01' high of theeenmtugel tYPeand sewed the tive displacement reciprocating plungertype, combined to realise the advantages and none of the disadvantagespi each.

3 i'eedwater temperature (as a result oi regenerative ieedwater heating)because the gases are expanded and cooled in the gas turbine.-aiter'leav- $235,233,? g a the db -flled August 21, um, and entitled'Fluid .i'orcing 25 advantageous aspects of h h degree i'eedwatersystem" I have dumbed e m a' co-pending application serial K01160288byvincorpomting the heater or placement This pump is comparatively I{$.52 fifigz z gfig z g fi agamt liquids at high pressure emciently-However in the feedwdte'r enters the boner at a comparatively a sizelarge enough for. a 5,000 horsepower plant 9 low temperature andrecovers heat simultaneously '3 speed a g gg g 'g 2 g from the fluegases and from the bled vapor irom mm per ca use an mtemadmtev stage ofthe mam propulsion tional tendencies during the admission stroke, soturbmea v great are the fluid accelerations involved.

This amusement of fed water heating and Therefore I prefer to "load'-this reciprocating 35 the employment of the exhaust gas turbineperfump? g a z mit regeneration and ieedwater heating up to fi gg f: t gt type 850 r'. for instance, yet maintain high boiler d a mumsefllciency and small boiler size. The regenerative vapor cycle improvesoverall powerplantefllci ency 40 when boiler eiiiciencyfls unimpaired'by its use, and due to the amount of steam bled oi! iron the vaporturbine 'at one or more portions, the actual qauntity. of outlet vaporto be condensed and therefore the size of the vapor condensers is Usingsteam as a working fluid, an outlet vapor temperature of 1250' 1'. andpressure of 3200 lbs per square hich may be'produced in the generatorwithout dimculty arising from the use of such triiugal pump. in order torotate the reciprocating pump'ata speed even as high as 8,000revolutions per minute without cavitation. The pressure from thecentriiugal pump is efleotive tion in, the positive displacement pinupcylinders during the admission strok'e, and indeed is suiflcient to holdthe pumping 'pltmgers against their rotating and oil pressure-adjustableactuating cam so that return springs are not neces-v sary for theplungers. On account of the high speed or operation a comparativelysmall reciprocating pump may then be employ and the of th worm theremremt muted utilisation of the described pumping. technique practically byboiler construction. 7 g V The useof circular flns on the economizertube helix makes it capable of withstanding reat pressures. and the flnsincrease the eii'ective gas swept area for eflicient heat absorption.The economizer line are shrouded so that the gases of combustion mustpass between the flns to remove stagnant' gas areas. The .shrouding ofthe flnsv 60 also prevents change of cross sectional flow 'area.ofl'ered to the gases as they progress from one loop or the tubehelixto the next, reducing the ratio or flow resistance to heat transmission.

A further modification which improves .the ei-- pump weight per powerplant horsepower out- 4 put in an exemplary case, with a pump eiiiciencyotover 90 percent. a Feedwater at 300 pounds per square inch pressingle-.t s centrifugal pump operated between stance; although the pumpeiflciency is not high under the circumstances. Because the requiredabout 10 percent that o! the reciprocating pump the inefliciency is,nota practical disadvantage,

weight is embodied in an arrangement tor evacuating the insulation space0! the generator casing by a vacuum pump. or in particular by the vacuumpump'tor the power plant cond 10 The condenser and the casing are,tor-instance,

maintainedat about; 2 inches mercury absolute pressure.Therarifled'airnithinthecasinginsulating space is essentially han-conductive.

to the'high boiler working pressure and below the 1g circination thereed pump must deliver in the increase in preciably in the loading pump.7 As an emergency measure to prevent overheating in the centrifugalpump, a by-pam ductcom' troliedinopeningbyathermostaticvalvscomand ,thepowerpiant working fluid exhaust condenser. The thermostatic valve opensat a predetermined temperature oi the discharged fluid, saturationtemperature, rate or discharge tram the in preventing vacuum formationor vapor i'orma-- aflords a weight ratio of as low as .003 pound.

22,000 and 45,000 revolutions per minute, !or-in-.

,andordinaril'ytheteedwaterisnotheated ap-.

municates between the discharge of the pump light and compact andcapable of discharging square inch from a separate high speedcensure-is'readily provided for loading by a smallpressureriseintheloadingpmnpknotover allowing an centrimgal J tributionto the fuel fed to the boiler, effecting a pump due to by-pass flow tothe condenser. This arrangement resists temperature rise in thecentrifugal pump, beyond the temperature setting, and is primarily ofvalue to prevent vapor generation by fluid friction during occasionswhen the positive displacement pump is regulated through its oilpressure operated system for adcylinders. This novel method cooperatesin the prevention of undue fluid friction tending to produce cavitationor vapor formation, for the valve is not operated as a result ofhydraulic suction acting upon it as is the case when ordinary I inletcheck valves are used.

A shaft extends downward from the rotating pump plunger drive cam,between the grouped parallel pumping plungers and forms a singlerotating port valve adjacent to the closed end of the cylinders forcontrolling the opening between each cylinder and' the inlet and outletducts of the pump.

This valving method permits one valve to suffice for inlet and outletcontrol of all cylinders of the pump. Furthermore the rotary valve doesnot involve actual metal to metal contact at the valving ports. It iscentralized by comparatively remote lubricated bearings permitting asmall clearance, insufficient to allow appreciable fluid leakage,nevertheless the clearance is existent to prevent wear or sticking. 7'

The oil supply system of the generator is combined in operativerelationship with the fuel system and feedwater supply system of thegenerator.

Variation of feedwater supply rate is accomplished subject to demands orconditions in the generator by action of oil pressure upon the drivingcam of the feedwater pump to change the cam angle and as a result theplunger stroke. The control is continuous and does not at any timeinterfere with the true harmonic motion of the pumping plungersfollowing the rotatingcam; The hydraulic oil supply simultaneously,lubricates the working faces, gears, etc. of the accessory portions ofthe generator. Heat contributed to the oil by friction is salvaged'byconslight increase in plant efliciency. r

The fuel is preferably fed to the burner nomle at a pressure of about250 lbs. per square inch. Because gear pumps are highly compact andsuitable for operation at this pressure without objectionableslip, Iprefer to use a gear pump for the fuel as well as for the lubricatingoil system. r n; A However fuel is a? poor lubricant. Accordingly theinventionv combines the oil pump-and the fuel pump structures so thatgear tooth wear which might otherwise arise in the fuel pump due to theinadequatelubricating Qualities of the ins is eliminated. JI'he oil pumpand the fuel pump are constructed as superimposed units with common gearshafts so that torque is carried through the lubricating pump gearsdirectly to the individual fuel pump gears, align! ing the latter gearsrotatively. No tooth pressure is delivered from one gear to the other inthe fuel pump as a result.

The novel arrangement of the generator incorporating the generationaccessories such as the blower, feed pump gas turbine, etc. in one endthereof produces the most direct interconnection of the flow systems,and a very rigid yet light structure withal. The axial shaft bearing thegas turbine, the blower impellers, and the driving gear for theremaining boiler accessories is rotated at high speed such as 15,000revolutions per minute at sea level, and 30,000 revolutions per minuteat altitude. The axial shaft permits perfectly symmetrical diffusers tobe placed around the impellers,, and a perfectly symmetrical turbinenozzle ring to discharge into the turbine buckets. This increasesthermal efficiency of the blowers and turbine. Also the diffusers andthe nozzle ring remain within the bounds of the boiler casing diametersimpli-. fying boiler construction and decreasing overall dimensions. IQ

The axial shaft isgeared down toa relatively low speed shaft, at onefourth speed for instance for the secondary feed pump, the oil pump,fuel pump, turbine speed governor, and

magneto. A powerful and compact worm gear arrangement is provided byhaving the shafts placed normal to each other. The accessories arepancaked one on top of the other along the slow speed shaft providingcompact and rigid interconnection, also conforming generally to theexternal cylindrical form of the vapor generator casing, and yet eachaccessory is readily removable from the boiler without disassemblythereof;

The superimposition of accessories along the normal shaft facilitatesdriving these several units with only one gearset and with a minimumamount of driveshaft. The 4 to 1 gear reduction is readily accomplishedin small space by the worm g'ea'rset, preferablyof the cone type.

A companion gearset on the axial shaft drives a second normal shaftproviding compact high speed drive of 1 /2 to 1 for instance for theloading pump impeller. I Y

. In Figure 1 the'generator is shown in section along its ,axis; Air forcombustion enters an inlet l of a centrifugal blower impeller Z for afirst stage compression and is reversed in a'diffuser 3 to reenter aninlet 4 of a centrifugal rblower impeller 5 for a second stage compreseslon. The impellers 2 and 5 are rotatively joined to a gas turbine wheel8 and to a drive shaft 45 along acommon axis A-A- of the generator.

A boiler casing l5 and a flue casing I join end to end to form anelongated cylinder to support the diffuser 3 of the impeller 2 and adiffuser G of theimpeller 5. 'The shaft 45 isborne in the casing I bymeans of the diifusers 3 and 6.

Compressed air from the diffuser i is con-1 ducted alongan annularpreheater passage 18 bounded by an'inner cylindrical shell l9- and anouter cylindrical shell H, in the direction of some'vanes 200i a boilerend cover 28. The

air; reverses in directionagainst the cover and passes into an axial andcylindrical combustion chamber 34.

' Fuel is injectedinto the chamber 34 by an axial nozzle which piercesthe cover 28 and casing end lid 26 thereof, and this fuel nozzle 21forms a conical spray 30 for mixture with the incoming air. The fuel isburned as it progresses within a combustion shroud 32 ing the chamber34. Adjacent to a discharge lip 33 of the shrould 32 another reversal offlow takes place. The burning charge-is deflectedfrom an end cone 24 andpasses back around the exterior of the shroud 32 and along an axialhelical tuhe superheater 23, within an annular space 35. V

The superheater helix is constructed of spaced l0 loops of a tube 40,but 'the space between the tube vibration. Yet the strap is able toexpand 0 longitudinally and radially with the tube durin temperaturechanges. Finally thecombination of the helical tube and the strap forman imperforate barrier to guide the gases of combustion within the space35 in the direction of a boiler economizer 38.

At a region 36' of the superheater and adjacent to the lip 33 it ispreferable to crowd the loops of the tube 40 and to eliminate the strapaltogethen at this point, for 1 the vicinity of the combustion chamberoutlet the gas temperatures run relatively high and the heat pickup ofthe superheater is so great at this location that an extension of theheating surface is unwarranted orundesirable. At the region the 35 loopsof the tube are welded together and are welded or bonded to the edge ofthe cone 24.

The heat contribution of the gases of com-.

bustion-to the economizer is accomplished by penetration of the gasesbetween some cir- 40 cular transverse fins 42 of the helical tube 39 ofthe economizer 38; The gases are laterally restrained to pass betweenthe fins by the surrounding shell I9 and by the superheater 23 which isclosely encompassed by'the economizer 38. The 5 shell I9 is corrugatedto conform to the circular shape of the fins. The superheater 23 is alsoin effectcorrugatedtoconform to the peripheral form of mem because thestrap 31' is thinner" than the diameter of the tube 40 yet wound at thesame pitch diameter. The tube to and the tube 39 are provided with thesame helicalpitch and staggered fins 42. r a I The gases of combustionhaving swept and heated the economizer next expand iii a turbine nozzlering 43 attaininghigh velocity therein. The gases strike against somebuckets 9 of the wheel 8, rotate the wheel, and drive the shaft 45. Thespent gases from the wheel are conducted within the casing I, and inthermal contact with the diffusers 5 and 3, to an outlet flue 44. Amethod of cooling the wheel 8, and of coolso that the strap 31 may'abutthe ing a turbine bearing 25 is embodied in an air by-pass duct 20, in acooling space 2I adjacent to the wheel, and in a plurality of spillholes 22 of the cone 24. This comprises a fiowsystem for relatively coolair to passfrom the diffuser 6 to the space 35. During its passage theair absorbs heat from theswheel and the bearing by thermal contact andenters the space 35 in highly heated ,condition to combine with unburnedfuel particles which have impinged upon the cone 24.

Insulation of the boiler casing is accomplished by evacuation of a spaceI6' bounded by the'shell 75 I1 and the casing I5, through a vacuum ductI I.

bound-' Feed liquid to be generated as working vapor is admitted at aninlet of the economizer tube 39, transferred at the outlet end of theeconomizer to the superheater tube 40, and heated to 1250 F. forinstance. The conditioned vapor 5 issues from the superheater tubeoutlet I0 to be, used in the main propulsion turbine. The heating of theliquid in the economizer 38 is abetted by a vapor filled helical tube-4|housed within the economizer tube 39. The vapor for the tube M isextracted from an intermediate expansion stage of the power plant mainpropulsion turbine. After delivery of heat to the feed liquid, throughthe walls of the tube H, the vapor becomes condensed as a result andissues as liquid from an outlet I3 adjacent to the economizer inlet I2.

. The tube M is substantially concentric with the tube 40 and theworking fiuid being conditioned in the economizer 38 flows within theannular passage formed between the tubes.

/ In Figure :2 I have shown the loadingmump in section along its axis3-3. An accessory housing 52 surrounds a worm 50 of the shaft 45, fordrivinga gear 5I of a shaft 59. The shaft 59 is located along the axis3-3, which is normal to the axis A-A; and is aligned in a bearing I0.

The shaft 59 revolves a centrifugal impeller 56 having vanes SI forforcing the liquid from an inlet 64 through some diffuser vanes 62 intoa 3 scroll 03. The scroll 63 is defined by a lower pump body 80 and byan upper pump body 58. Some hollow chambers and 89 are provided in thebodies for weight reduction. A labyrinth 5I retained in the body 50engages the inlet flank of the impeller 56 to prevent transmission ofpumped liquid back to the inlet 64.

A labyrinth 55 mating with the opposite flank of the impeller 58 andseated in the body 60 retards loss of pumped liquid out a leakage duct54.-

The body 58 is attached to the housing 52. A buffer duct 53 in the body58 leads to the shaft 59 and separates, the bearing I0 from the leakageduct54. The duct 53 is supplied with compressed air to preventintercontamination between the liquid in the duct 54 and the lubricantin the bearing 10.

Figure 3 is a section through the impeller and diifusermf the loadingpump of Figure 2 taken 50 normal to theaxis 3-13. The scroll 83 dischar'ges liquid under pressure to an outlet 65 for transfer to thepositive displacement feed pump.

In Figure 4 are illustrated in section along a common 'axis thereciprocating second stage feedwater pump, the oil pump and the fuelpump of the generator, mounted in tandem. Within the housing 52 a wormI00 of the shaft 45 drives a/ gear I22 of a shaft I08. The shaft-l06 hasan axis CC normal to the axis A.-A of the shaft 45.

The gear I22 rotates aplanar face cam I20 about the axis 0-6 by means ofa projecting rail I23 mating with the cam. The cam I20 is'angularlyadjustable with respect to the gear I22 for regulating the'stroke ofsome plungers I05 clustered about the shaft I06 and having axes parallelto the axis C-C. Some pivotal segments I2I transmit thrust from thewobbling cam to the plungers.

The plungers I05 are provided with some oil packings I53, a seepagespace I54, and some feed liquid packings II I adapted to reciprocateharmonically within some cylinders II3 of a pump body H4 and to eifectpumping actioneunder influence of the cam m. A duct bleeds the space m.

Feed liquid from the loading pump outlet 65 enters a chamber H3 underpressure. The shaft I06 is projected downward within the body II4between the pump cylinders and within a lubricated bearing M2 foralignment. Adjacent to the chamber II8 the shaft I06 is slotted to forma liquid admission port H1 and a liquid discharge port II6. As the shaftI06 rotates the port I" successively connects the chamber II8 to some ofthe cylinders II3 for liquid admission thereto. Simultaneously the portII6 registers with the remaining cylinders to effect a vent to a dis-.,

charge duct II9 for expulsion of feed liquid at high pressure;

The port H6 bears fixed rotative phase relationship to the cam I20, sothat some cylinders H3 are ported to the chamber IIB only while theirrespective plungers are riding down the cam and while there can be anincrease of volume in these cylinders as these plungers-follow the cam.In conformity with this arrangement the port 1 also is fixed rotativelywith respect to. the cam I20 so that communication between the remainingcylinders H3 and the discharge duct II! is effected only as thecorresponding plungers thereof rise upon the cam producing a compressionin these cylinders.

The plungers I05 and the segments I2I are held in contact with.the camI20 as a result of fluid pressure in the chamber I I8, which issufflcient to cause the plungers to follow the cam located the governorand magneto assembly I42 actuated by the shaft I06.

- An air gap I50 between the body I31 and the ,body I38 prevents undueheat transmission from the oil pump tothe feed pump. Elevatedtemperature is present in the oil pump as a result of viscous frictionwithin the housing 52. This heat 1 is carried tosthe oil pump. Heatingof the fuel pump would tend to cause vaporization of the fuel'which issomewhat volatile. It is therefore advantageous to expel the heat of theoil into 'the fuel, not at the fuel pump, but beyond the fuel pump in aheat exchanger 2", shown in I32 extending through the body I31 and thebody I30 to some similarly arranged mating gears I33 of the fuel pump,which mesh with the gear I34 between the body l36'and the body I33 toaccomplish fuel pumping. However the fuel pump gears are constructedwith greater clearance so as to engage without actual contact becausethe fuel pump gears are guided rotativelythrough the shaft I06 and theshafts I32 by the oil pump I20 even during its greatest angularity andspeed of rotation.

The pump body H4 and a cover body I36 are attached to the housing 52.Theangular trim between the cam l20 and axis C-C is determined by theelevation of a wedge I01 movable by a hydraulic piston I50 in aninternal cylinder I5I of the gear I22. The piston I50 and the cam-I01are slidable along the shaft I06. The wedge I01 acts between the shaftI06 and the cam I20 to vary the angle of the 'cam. Thus oil pressureadmitted to a groove I25 of the body I36 supplies an orifice I24 passingfrom the external surface of the gear I22 into the cylinder I5I to theupper side of the piston I50. Depending on' the amount-of pressureproduced in the cylinder.

the pistonassumes one of an infinite number of gositio'ns between fullyraised and fully lowere U The greater the "rate of oil admission to thegroove I25, the further the piston I50 is depressed, lowering the wedgeI01 and increasing the angularity of the cam, thereby increasing theoutput of the pump. Oil leakage past the piston 1 I50 escapes into thehousing 52 where it serves to lubricate the gears and various slidingsurfaces contained therein.

Superimposed upon the cover body. I36 which absorbs thrust of the gearl22 and of thescam I20, is an oil pump body. I31. The" shaft I06extends. upward from the gear I22 through the body I36 and the body I31.Theshaft l06 rotates-an oil pumping gear I30 between the body I36 andthe body. I31.

Superimposed upon the body I31 is a lower fuel 1 pump body I38 and anupper fuel pump body gear I34 between the two.

I39. The shaft I06 protrudes upward-through these latter odies andrevolves a fuel The shaft.l06- extends still further upward into achamber I 4| of a body I40 attached to the top of the body I33. Withinthe chamber I4I. are

gears I3I.

The axes X- -X and Y-Y of the shafts I32 are parallel to the axis C-C.

In Figure 5 a diagrammatic representation of the vapor generator andassociated power plant units is shown.

Conditioned working" vapor from the generator outlet I0 passes to a highpressure turbine20I. A throttle valve 206 is located in' the outlet I0for control of the vapor supply to the turbine.

From the tubine 20l a portion of the partially expanded vapor passesinto a low pressure tur. bine 202 and the reminder to the regeneratortube" H of the generator. The turbine 20I and the turbine 202 drive anairscrew 200 by a shaft Exhaust working vapor from the turbine 202 isconducted along a pipe 204 into a condenser 205. A'feed liquid ductI80supplies the inlet L of the loading pump with condensed working vaporfrom thecondenser 205. -A vacuum pump I10 driven by the shaft 59 of theloading pump evacua'tes the space I6 of the generator heat insulafiingcasing l5and the condenser I05. Vac- I1.I of the pump I10.

uum is produced in the duct II through a returncheck valve I12 and inaduct I14 communicating with the condenser 205, by a vacuum conduitIgnition of the fuel ber 34 is accomplished by a' spark 250 between theburner nozzle 21 and an electrode I63. The electrode is supplied hightension current along a lead 162 of a magneto I425 grounded by a leadI60. The magneto I42]; and a speed; governor -I42a are revolved by theshaft I06.

A by-pass duct between the outlet of the loading pump' and the condenser205. A thermostatic valve I95 in in the combustion cham-.

I36 forms a communication the duct I36 and adjacent to the outlet 65ordi narily remains closed'to prevent try-passing of' feed liquid fromthe loadin denser. However. if the temperature pump to the conin theout- Jet 65 reaches a predetermined value oi 200 F.

6 aaaaese' For regulation of the presure in the genera tor combustionchamber 34 there is provided a waste gate I92 for bleeding gases ofcombustion 1'0 ;from the nozzle ring 43. As the gate I3! is opened gasesof combustion tend to by-pas's the turbine buckets 9 and to allowreductionpf the speed of the turbine. But if the gate I32 be closed thebuckets 9 receive a greater flow of ases of combustion from the nozzlering .43 and .the turbine speed is increased. The control of the gate"2, subject to sensitive devices to be described, is therefore capableof varying blower speed and of regulating the back pressure acting uponthe gases of combustion leaving the economizer.

A representative method for controlling the gate I92 comprises anevacuated bellows 352 seated withinza chamber I of a pressure casing353.,

The casing 353 is connected to the combustion,

chamber by a duct 3". If the combustion chamber pressure tends to risebeyond a predetermined absolute pressure value, such as '35 pounds persquare inch for instance, the bellows 352 becomes go abruptly compresedand a link 35,4 extending out of the casing I from the free end of thebellows transfers the motion to the gate I52 efleoting an openingthereof, to restore the combustion chamber pressure to its normal value.

However if the combustion chamber absolute pressure tends to drop belowthe predetermined normal chamber the and the link 3" is thrust by thefree end of the bellows in the opposite direction to close the gate I92.The closure of the'gatev I92 increases the back pressure acting upon thegases issuing from the economizer because then all or more of the gasesof combustion must pass through-the nozzle ring 13 which constitutes adefinite flow restriction at any given supply pressure. The turbine isac celerated by the greater rate of gas passage through the ring 43causing a greater pressure rise in the generator air blowers due to thegreater operational speed thereof. The combination 'of I 5 the increasedback pressure upon the gases issuing from the economizer, and thegreater blower speed cause a restoration of the combustion chamberpressureto thenormal value.

A second representative method for controlling 55 the gate I92, whichmay be described in action by assinning that the dotted portion of thelink 35l has been removed and that the link 3 no longer acts upon thegate I92, comprises a tie rod I9I from the gate to a middle pin 30! of afloating o link 306 having an end 3 attached to an evacuated bellows303, and an end 301 tied to the speed governor I 42a by a lever arm I90.

Increase of operational altitude of the aircraft tends to cause thebellows 303 to expand abruptly 65 raising the end 304 of the link 354',and consequently moving the rod I9I to close the gate m.

However as the speed of the gas turbine increases as a result of thisclosure, the speed governor 2a lowers the opposite end "Mending toreduce the 70 degree of closure of the gate "2.. The points ofattachment to the link 308 are spaced in a proportionality whichproduces a substantially constant absolute pressure in-the combustionchamber 34 as the bellows 393 and the governor Inc 7 compensate forchange in atmospheric pressure bellows expands abruptly V 'and inturbine speed,'during' ascent of the aircraft.

As the aircraft descends the motion imparted to the link 3" is reverseddue to collapse of the bellows and due to raising of the arm I by the 5governor. This maintains the combustion chamber absolute pressuresubstantially constant.

-For regulation of (the worldng vapor output of the'vapor generator,there is provided an adjustment to the bellows 333, as also can beprovided :10 on the bellows 382. to allow the control of combustionchamber absolute pressure to be effected at a lower predetermined level,such as 25 pounds per square inch regardless of the operational altitudeof the aircraft. This maintenance corresponds 15 to low cruising poweroutput at all altitudes and provides substantially constantcruisingpower. The adjustment embodies a threaded rod 3| supporting thestationary end of the bellows 393, mounted in a post"! and rotatable bya knob 20 m, to cause a raising or lowering of the bellows as the casemay warrant. correspondingly the combustion chamber constant absolutepressure control level is raised or lowered. It is obvious that thiscontrol may be accomplished by auto- 2 matic means brought to act uponthe knob up,

as well as manual means, for conditions such as generator working vaporpressure or speed of the propeller 299 are available to effect anapproprirate motor mechanism on the knob to maintain a .80

gears I33 and I34, and a fuel duct 240 from the gears I33 and I34 to theheat exchanger 2| I.

In the oil flow system I provide an inlet duct 23!! which may draw oilfrom a drain 2"! of the housing 52 and which supplies the oil pumpinggears I39 and I3I. The oil is forced along a duct 0 2 to the heatexchanger 2| I. Beyond the heat exchanger the oil may travel underpressure in a line 2! 2 into the housing 52. However the oil may shuntthe line 2I2 past a variable throttling valve 2I3 into thegroove I25 forcontrolling the a position of the feedwater pump cam I10 and the liquiddischarge rate of the positive displacement pump. The means brought toact upon the valve 2I3 affecting the oil flow and the generator feedliquid flow are not shown. However it is cusv tomary in the art ofboiler control to re ulate the rate of feed liquid supply in accordancewith a generator conditionsuch as pressure or, temperature at a regionof the boiler tube.

In Figure 6 a graph of fluid pressure ordinate values plotted againstflow distance abscissal values is presented for the generator.

It is shown by a solid line representing sea level conditions and by adotted line representing conditions at a pressure altitude of45,000 ft.,that combustion air for the generator is given hyper-adiabaticcompressions in the first stage impeller and diffuser thereof followedby a tem-,

perature rise at constant pressure due to heat in the economizer asubstantial drop of pressure of about 10 lbs. per square inch results.In the nozzle ring an.expansion is accomplished with drop of gastemperature to below atmospheric pressure. The gas temperature enteringthe ring is about 800 F. At sea level the gas temperature afterexpansion is approximately 560 F., while at 45,000 ft. altitude thetemperature after expansion is about 260 F. due to the greater expansionafiorded.

Within the turbine buckets there is a slight recompression or furtherexpansion as the case may be. The initial pressure of the air enteringthe generator is somewhat greater than the pressure of the fiue gasesleaving the flue casing because air is generally supplied from arelatively high pressure region adjacent to the aircraft, and it isarranged to expel the gases of combustion into a relatively low pressureregion adjacent to the aircraft.

Because the temperature of combustion within the boiler combustionchamber is very high, heat resistant material, such as carborundum, maybe advantageously employed for the shroud 32 of Figure 1. However I havefound that the temperature of the combustion shroud may be controlled tosome extent in high velocity combustion chambers by special distributionof the fuel and air, characterized by arrangement for an unbalancedmixture ratio either too rich or too lean and therefore at acomparatively low temperature to come in contact with the shroud. It isfor this reason unnecessary to cool the shroud with tube convolutionscontaining working vapor.

In Figure 1 the spiral course of the air and fuel flow along thecombustion chamber diagrammatically signifies that rich portions of thefuelair mixture are thrown centrifugally against the inner wall of thecombustion chamber providing a relatively cool protective layer.

The numericaldesignations in the various figures of this specificationare consistent throughout. I have endeavored to deal with representativeforms of the invention, for the invention may be actually embodied in avariety of forms of similar character. It is intended that the claimspresented herewith shall cover these various forms in the broadestsense.

I claim:

1. A vapor generation system comprising a. once-through boiler tubeswept internally by vapor at relatively high velocity and relativelyhigh pressure, said tube being enclosed within a pressure-resistingcasing and being swept externally by gases of combustion at highvelocity within said casing, a gas ing, a positive'displacement pump forfeeding liquid to said tube, a centrifugal type Pump for loading saidpositive displacement pump said turbine driving said positivedisplacement pump and said centrifugal type pump, a device sensi-,

tive to temperature of the feed liquid, and means for said device tovary the relative rate of discharge of said change-of velocity type pumpwith respect to said positive displacement pump.

2. A vapor generation system comprising a once-through boiler tube, acombustion space for heating said tube, a turbine operated'by gases fromsaid space, an auxiliaries shaft operted by said turbine, a variabledischarge positive displacement pump for feeding liquid to said tube, acentrifugal type pump for feeding liquid to said positive displacementpump, said positive displacement pump andsaid centrifugal type pumpbeing driven by said shaft, a device sensitive to thermal conditions insaid centrifugal type pump, means for said device to vary the relativerate of discharge of said centrifugal type pump with respect to saidpositive displacement pump, said positive displacement pump havingpumping plungers and a hydraulic adjustment for the stroke of saidplungers, a first pumping gear set for supplying oil to actuate saidadjustment, a second pumping gear set for supplying fuel under pressureto said space, some torque shafts extending between said first and saidsecond gear sets and maintaining a fixed rotary phase relationshiptherebetween, and said auxiliaries shaft driving said torque shafts.

3. A flow system comprising a consumer requiring varying quantities ofliquid at relatively high pressure, a positive displacement pumpconnected to said consumer, a fluid impeller of a type adapted todevelop fluid pressure by rotational velocity connected to said pump, aliquid supply source connected to said impeller, a conduit bypassingsaid impeller, a flow control means in-said conduitjand a deviceresponsive to temperature of the liquid being discharged from saidimpeller for regulating said means.

NATHAN C. PRICE.

turbine connected to said cas--

